Conventionally, in a case where, for example, a plurality of indoor units (fan coil units) are placed at such places as large-scale plants and buildings, a heat source system is utilized which supplies heat source water (cold water or warm water) from a heat source machine to these indoor units so as to air condition a plurality of air conditioning areas.
The heat source system is mainly divided into a heat source machine side and a load facility side (indoor unit side), and these sides are connected through a delivery pipe, which supplies heat source water from a heat source machine to a load facility, and through a return pipe, which returns the heat source water to the heat source machine via the load facility, thus constituting one circuit.
For example, the heat source water that is made to exchange heat inside the heat source machine passes through the delivery pipe and is delivered to the load facility by a load-side secondary pump. The heat source water is then made to exchange heat inside the load facility and is sent to a primary pump of the heat source machine through the return pipe. The heat source water sent to the primary pump passes through the inside of the heat source machine again and circulates inside the circuit.
During such operation, if the heat source machine is operated while water is not normally fed by the primary pump due to some sort of failures, the heat source water residing inside a heat exchanger of the heat source machine may be cooled and frozen, as a result of which the heat exchanger may freeze and burst.
Accordingly, the heat source machine is equipped with a flowmeter for measuring a flow rate of heat source water so that a flow of the heat source water is detected with the flowmeter.